Net radiation flux

Equations (4.120 and 4.116) demonstrate again that small values of G and H are desirable. Even with perfect thermal isolation, heat radiation is still present and limits the lower value of G. At the temperature difference AT between a bolometer and its surroundings, the Stefan-Boltzmann law gives for the net radiation flux A/ to the surroundings from the detector with the emitting area A and the emissivity 6 < 1... 

This is vaiid because the energy lost by body 1 is gained by body 2. The net radiation flux leaving body 1 can be expressed as ... 

The second material property is heat of gasification, L, defined as the net heat flow into the material required to convert one unit mass of solid material to volatiles. The net heat flux into the material can be obtained from an energy balance at the surface of the specimen. Typically, a sample exposed in a bench-scale calorimeter is heated by external heaters and by its own flame. Heat is lost from the surface in the form of radiation. Owing to the small sample size, the flame flux is primarily convective, and flame absorption of external heater and specimen surface radiation can be neglected. Hence, L can be defined as... 

Some specific studies on the measurement of heat losses and indoor temperatures in buildings deserve attention. In his review of the relative importance of thermal comfort in buildings, McIntyre considered that the mean radiant temperature was the most important parameter, followed closely by the "radiation vector," which is defined as the net radiant flux density vector at a given point and measures the asymmetry of the thermal radiation field in a room (97). Benzinger et al. characterized the mean radiant temperature, and asymmetric radiation fields, using a scanning plane radiometer, which maps the plane radiant temperature in a given space indoors (98). 

Another quantity of interest in the discussions to follow is the radiative flux vector qA(r) (W m sr ), which gives the net spectral flux of radiation along the preferential propagation direction in a given point. It is, in simple terms, intensity summed as a vector over all propagation directions... 

The Earth-atmosphere system emits thermal infrared radiation. The upward flux from the Earth s surface is —115 units. The cloud-free atmo.sphere emits —33 units back to the Earth s surface and —34 units out to space. The cloudy atmosphere emits —67 units back to Earth and —36 units out to space. Thus —70 units of infrared radiation leave the top of the atmosphere, balancing the net —70 units of. solar radiation penetrating the top of the atmosphere. The net upward flux of infrared radiation at the surface of the Earth is — 15 units, consisting of — 115 units emitted by the Earth and —100 units radiated back to Earth by the cloud-free and cloudy atmosphere. 

The incoming solar energy absorbed by the Earth is —44 units this is balanced by the net upward flux of infrared radiation of — 15 units, plus —6 unit loss by sensible heat conduction, and —23 unit loss by latent heat. The Earth emits — 115 units of infrared radiation to the atmosphere, whereas the atmosphere emits —170 units of infrared radiation, a net deficit of —55 units. Since the atmosphere absorbs —26 units of solar radiation, the net radiative loss from the atmosphere is —29 units this is made up for by the sensible and latent heat fluxes. The net radiative cooling of the atmosphere is thus balanced by the latent heat of condensation released in precipitation processes and by the convection and conduction of sensible heat from the surface. 

The mass here refers to the fluid constituent being observed, whether that be BOD, temperature, sediment particles, or other materials. The net mass flux enters the control volume by convection (velocities in the fluid) and molecular diffusion, assumed to follow a Fickian law as in Eq. (1). Internal sources and sinks may include deposition, chemical or biological reactions, attenuation of solar radiation, radioactive decay, or other processes. 

Fig. 4 displays net assimilation Pn, corrected by the intermolecular collisions between CO2 and water vapour, versus leaf conductance to CO2 (gc). For example, data on august 1 are given up to gc values between 0.2 and 0.23 mol m s, the gc dependence on Pn is almost linear and the slope of this line represents Ca-Ci. This justifies the model chosen. Canopy gas exchange and net radiation are given for the same day (Fig. 5). CO2 aerodynamic fluxes measured, toes, and calculated, Ocal, by the model are shown.

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